MOSCOW, April 28 (Reuters) - Rosneft Chief Executive Igor Sechin, on whom the United States imposed sanctions on Monday, said the measures would not harm the company's cooperation with its partners.

"I take the last steps by Washington as an appreciation of the efficiency of our work," Rosneft's press office cited Sechin as saying in a statement.

"At the same time we assure our shareholders and partners, including American ones, that this efficiency will not diminish and our cooperation will not be affected." (Reporting by Vladimir Soldatkin; Writing by Lidia Kelly, editing by Nigel Stephenson)